check all your settings. i have my backlight set for 50 percent brightness. and to shut off at 10 seconds. my batt don't last like it should. i ran a speedometer program once that kinda heated up the phone and ruined the batt a little. but with those settings. i can still keep up for the day. and my phone gets texted A LOT. the back light kills more then making a phone call.
check all your settings and shut down things you don't need and cut down on everything else.
the phone comes with an 1100 battery. i see 1000 batteries on the net. and some 1400's too. $50 will buy you a 1400. that's 30 percent more power.
my first windows mobile was a treo 700wx. the battery sucked all along. i was able to find a brand new replacement on the net for $10. and it kicked butt over the original battery. exact same battery.